As of the recent updates to the system (replacing the original Genie+), you should book your Lightning Lane Multi Pass well in advance of your trip. If you are staying at a Disney Resort hotel, you can purchase and make your first three selections up to 7 days in advance of your check-in date for your entire stay (up to 14 days). For all other guests, the booking window opens 3 days in advance of their park visit. The booking window opens at 7:00 AM ET on your eligible day. It is vital to book as soon as your window opens to secure the most popular attractions like Slinky Dog Dash or Peter Pan's Flight, as these time slots disappear quickly. Unlike the previous system where you had to wait until the day of your visit, this newer "advance booking" model allows you to plan your itinerary before you even leave home. If you miss the advance window, you can still purchase it on the day of your visit, but your choices will be limited to whatever remains. Remember that you can only hold three advance selections at a time, but once you use one in the park, you can book another via the app.